Hand, Foot, and Mouth Disease (HFMD) is a common viral illness that primarily affects children under the age of five, though older children and adults can also contract it. This infection is highly contagious and spreads easily, often in settings like daycares and schools. HFMD is typically mild and resolves on its own within seven to ten days, but it causes uncomfortable symptoms, including a characteristic rash and painful mouth sores. It is entirely possible to contract Hand, Foot, and Mouth Disease multiple times.
Why Reinfection Occurs
Reinfection with Hand, Foot, and Mouth Disease is possible because the illness is not caused by a single pathogen, but rather by a group of related viruses known as enteroviruses. These viruses are classified into different strains, or serotypes, each capable of causing the same clinical symptoms. The two most frequent culprits worldwide are Coxsackievirus A16 and Enterovirus 71, but numerous other serotypes, such as Coxsackievirus A6, are also common causes of HFMD outbreaks.
The body’s immune system mounts a defense specifically against the particular serotype that caused the initial infection. This protection is typically highly specific and does not extend effectively to the other serotypes, like Enterovirus 71 or Coxsackievirus A6.
Since a person can encounter any of the several dozen potential causative serotypes throughout their life, they remain susceptible to infection from any strain they have not yet encountered. For example, a child infected with Coxsackievirus A16 one year could easily be infected with Coxsackievirus A6 the next, leading to a second, distinct episode of Hand, Foot, and Mouth Disease.
Immunity Gained After Infection
The immune system does acquire a permanent defense against the specific viral strain that caused the initial illness. This is known as serotype-specific immunity, meaning that once a person recovers from a Coxsackievirus A16 infection, they are generally protected for life against that particular serotype. This acquired immunity is crucial for controlling the spread of that exact virus.
The lack of broad protection across different enterovirus serotypes is the key factor that permits reinfection. While the body builds a strong, lasting shield against one strain, it remains vulnerable to the others that can also cause Hand, Foot, and Mouth Disease. Therefore, a second or even third episode of the illness signifies exposure to a completely different viral serotype.
A second infection is sometimes less severe than the first, possibly because the immune system may still offer a small degree of cross-protection against related strains. However, the severity of any HFMD case can also depend on the specific serotype involved. Enterovirus 71, for instance, has historically been associated with a higher risk of complications than Coxsackievirus A16.
Recognising the Symptoms
Identifying Hand, Foot, and Mouth Disease relies on recognizing a specific set of clinical signs that typically appear three to six days after exposure to the virus. The illness often begins with non-specific symptoms like a fever, reduced appetite, and a general feeling of being unwell. A sore throat is also a common initial complaint, particularly in children.
The most distinctive features develop after the initial fever subsides. These include painful, blister-like sores in the mouth, which can appear on the tongue, gums, and cheeks. These oral lesions often make it difficult and painful for a person to eat or drink.
Simultaneously, a rash appears, most commonly as flat or slightly raised spots, sometimes turning into small blisters, on the palms of the hands and the soles of the feet. This rash is usually not itchy, which helps distinguish it from other viral rashes, and it can also appear on the buttocks.